This invention relates to a method for producing a macroporous cross-linked copolymeric lattice which is capable of adsorbing hydrophilic and lipophilic fluids. The copolymer is a powder which is a complex structure consisting of unit particles, agglomerates, and aggregates, which can be defined as a lattice.
The concept of producing spheres or beads by means of suspension polymerization techniques is well known in the prior art. An exemplary one of such processes is disclosed in U.S. Pat. No. 2,809,943, issued Oct. 15, 1957. However, it was found that when a material was added which is a solvent for the monomers, but acts as a precipitant for the resulting polymer, a novel form of bead was provided containing a network of microscopic channels. This discovery is set forth in U.S Patent No. 4,224,415, filed July 18, 1958, issuing some twenty-two years later on Sept. 23, 1980. In this patent, beads are produced ranging in size from about 350 to about 1200 microns. Typical monomers include divinyl toluene, diallyl maleate, and triallyl phosphate. The precipitant employed is an alkane, acid ester, or alcohol.
This technology was expanded and the precipitant was variously described in the patent literature as a diluent, porogen, active ingredient, solvent, functional material, and volatile agent. For example, in U.S. Pat. Re. No. 27,026, issued Jan. 12, 1971, porous beads of a diameter less than ten microns are disclosed. Among the monomers used to produce the beads are ethyl methacrylate, divinyl benzene and ethylene glycol dimethacrylate. In U.S. Pat. No. 3,418,262, issued Dec. 24, 1968, there is described a bead characterized as having a rigid sponge structure, and wherein the porogenic agent employed is an acid such as stearic acid. Intermediates in bead form were produced in U.S. Pat. No. 3,509,078, issued Apr. 28, 1970, using polymeric materials such as polyethylene glycols as the precipitant material during the in situ suspension polymerization process. The macroporous character of such bead construction is graphically portrayed and illustrated in FIG. 1 of U.S. Pat. No. 3,627,708, issued Dec. 14, 1971. Beads termed "pearls" are produced and containing active ingredients therein such as water or various alcohol ethers. The pearls are crosslinked to the extent of about twenty percent. In U.S. Pat. No. 3,637,535, issued Jan. 25, 1972, beads with a sponge structure are said to be capable of being compressed to an imperceptible powder. These beads are capable of being loaded with as much as 200-300% of active ingredients such as white spirit, and benzin. A rigid porous bead of a trifunctional methacrylate is taught in U.S. Pat. No. 3,767,600, issued Oct. 23, 1973. Such beads have a size of 10-900 microns, and various other monomers which can be employed include diacetone acrylamide, and ethylhexyl, hydroxyethyl, and hydroxypropyl methacrylates. Paraffin wax in an amount of 5-100% is used to form the microscopic network of channels in U.S. Pat. No. 3,989,649, issued Nov. 2, 1976. The wax may be removed from the bead structure by solvent extraction.
While many of the foregoing U.S. patents relate to ion exchange technology, a bead similar to those previously described is employed as a carrier for enzymes in U.S. Pat. No. 4,208,309, issued June 17, 1980. Such beads are of the size of about 0.1 mm. U.S. Pat. No. 4,661,327, issued Apr. 28, 1987, describes a macroreticular bead containing a magnetic core. The use of hard crosslinked porous polymeric beads in cosmetics as carriers is taught in U.S. Pat, No. 4,724,240, issued Feb. 9, 1988, wherein various emollients and moisturizers are entrapped therein. These beads are said to be capable of entrapping materials such as 2-ethylhexyl oxystearate, arachidyl propionate, petroleum jelly, mineral oil, lanolin, and various siloxanes. The size of the beads ranges from 1-3,000 microns. Typical monomers include ethylene glycol dimethacrylate, lauryl methacrylate, trimethylol propane trimethacrylate, and dipentaerythritol dimethacrylate. "In situ" hydrophobic powders and "in situ" beads may be produced in accordance with the teaching of this patent. Beads having a rigid sponge structure are also described in U.S. Pat. No. 4,690,825, issued Sept. 1, 1987, and wherein the beads function as a delivery vehicle for a host of materials including pigments, vitamins, fragrances, drugs, repellants, detergents, and sunscreens. The beads have a size of 10-100 microns and are preferably of a monomer system of styrene-divinyl benzene. Crosslinking is said to range from 10-40 percent.
The foreign patent literature includes West German Offenlegungsschrift No. P-2608533.6, published Sept. 30, 1976, and wherein porous polymeric beads produced by "in situ" suspension polymerization are provided, and which are adapted to release perfumes. A controlled release of the fragrance is disclosed, providing utility for such beads in the home, automobiles, airplanes, railway cars, hospitals, classrooms, conference centers, and gymnasiums. Canadian Patent No. 1,168,157, issued May 29, 1984, describes hard, discrete, free flowing, bead constructions in which the beads entrap a series of functional materials which can be incorporated into toilet soap, body powder, and antiperspirant sticks. The Canadian Patent, it is noted, is the equivalent of European Patent No. 61,701, issued on July 16, 1986, both of which are foreign equivalents of the parent case of the '240 patent. In European lnternational Publication No. 0252463A2, published Jan. 13, 1988, there is disclosed a bead having a hydrophobic polymer lattice, and which entraps numerous non-cosmetic materials such as pesticides, pharmaceuticals, pheromones, and various categories of chemicals. Steroids are entrapped, for example, in the porous beads of PCT International Publication No. WO-88/01164, published on Feb. 25, 1988. The steroids are adrenocortical steroids or various anti-inflammatory type steroids. It should therefore be apparent that what began as a simple ion exchange bead concept has rapidly grown into a technology of widely varied application.
In accordance with the present invention, copolymer powders are produced by novel processes not believed to be taught in the prior art, as exemplified by the foregoing patents. Those patents, in general, relate to suspension polymerization processes for the production of porous polymeric and copolymeric spheres and beads in which the precipitant is present during polymerization. These are defined as an "in situ" process. For example, U.S. Pat. No. 4,724,240, while disclosing beads and spheres produced by "in situ" suspension polymerization techniques in one embodiment, also describes a process involving "in situ" precipitation polymerization technology, and in which there is produced powder-like materials, in contrast to beads. The PCT International Publication, while a suspension polymerization system, can also be defined as a "post adsorption" process in its use. In this variance, a volatile porogen is included which may be removed by extraction and evaporation, resulting in empty beads. The beads can be loaded with diverse active ingredients, as desired, at subsequent times. "Post adsorption" techniques are more attractive because of the flexibility in the selection of active ingredients that can be subsequently entrapped, whereas in the conventional "in situ" systems, the porogen polymerized "in situ" remains in the final product.
Thus, according to the prior art, hydrophobic crosslinked porous copolymers in particle form can be produced by at least three distinct processes. One process produces beads by "in situ" suspension polymerization, and this process is shown in Example 4 of the '240 patent, and in U.S. Pat. No. 4,690,825. Another process produces beads by suspension polymerization but the beads are "Post adsorbed" with an active ingredient after the volatile porogen is removed. This process is shown in the PCT International publication. In a third process, powders are produced by "in situ" precipitation polymerization, and this process is shown in Examples 1-3 of the '240 patent.
What has been accomplished in the present invention, however, is a unique concept differing from all of the foregoing methods, and wherein hydrophilic-lipophilic post adsorbent powders are produced. In contrast to the prior art, the powders of the present invention are capable of adsorbing lipophilic fluids, as well as hydrophilic fluids and liquids having a high surface tension such as water. The powders of the prior art have only been capable of adsorbing low surface tension liquids.